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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Algae and Fungi for Oil Production Using Papaya, Albizia, Sugarcane Bagasse and Testing Feedstocks in Anaerobic Digesters

Location: Tropical Plant Genetic Resources and Disease Research

2013 Annual Report


1a.Objectives (from AD-416):
The objectives of the research are: 1: To optimize the production of biofuels from papaya waste via the use of heterotrophic algae (Chlorella prototechoides), and characterize the oil for its potential use as biodiesel and higher grade fuel. 2: To produce biofuel from adapted oleaginous fungi that use cellulosic material from papaya and albizia wood as a carbon source. 3. To utilize biofuel in anaerobic digesters that could be adapted to the farm scale level in Hawaii.


1b.Approach (from AD-416):
The proposed research falls under our broad ‘Zero Waste’ approach to make agriculture in Hawaii more profitable and address food and energy security issues in Hawaii. This project utilizes agriculture wastes and other outputs as feedstock for producing biofuel via the use of heterotrophic algae/fungi and bioenergy from anaerobic digesters. Objective 1: To optimize the production of biofuels from papaya waste via the use of heterotrophic algae (Chlorella prototechoides), and characterize the oil for its potential use as biodiesel and higher grade fuel. We will refine the production conditions, and analyze the properties of the oil and its potential usefulness for biodiesel and higher grade fuel. The algae meal will be tested as a feed for fish in a separate study.

Objective 2: To produce biofuel from adapted oleaginous fungi that use cellulosic material from papaya and albizia wood as a carbon source. Our collaborator, BioTork LLC, has successfully adapted three oil producing fungi to grow crystalline cellulose and also on wood grounds of albizia (Falcataria moluccana), and on sugarcane bagasse. PBARC will optimize the conditions of these fungi to grow on cellulosic solids of papaya ,wood of albizia, and sugarcane bagasse.

Objective 3. To utilize biofuel in anaerobic digesters that could be adapted to the farm scale level in Hawaii. We will focus on identifying feedstocks, and on optimizing conditions that selected microbes will efficiently digest feedstock combinations under anaerobic conditions. Some of the possible feedstocks are wastes from papaya, sweet potato, guava, waste from other fruits (lychee, longan, mango, etc.), and albizia.


3.Progress Report:

The overall goal of this project is to produce biofuel from heterotrophic algae or fungi that use waste products from agriculture systems or regional plant material that are weedy and widespread.

The first objective was to produce biofuel from heterotrophic algae (Chlorella prototechoides) that use papaya fruit culls as a carbon source. The laboratory scale phase of the project has been completed (up to 5 L). We are consistently achieving 50% oil/dry weight (more than 5x the amount of when the project first began). We have made significant progress in using papaya as a feedstock for algae under laboratory conditions and are getting ready to move towards the mini-pilot plant scale. We currently have a 30 L bioreactor for scaleup and are in the process of ordering a 150 L working volume bioreactor.

The second objective is to produce biofuel from adapted oleaginous fungi that use cellulosic material from papaya and albizia wood as a carbon source. Oleaginous fungi that have been evolved on crystalline cellulose by our collaborators, BioTork have been received by Pacific Basin Agricultural Center (PBARC). We have commenced laboratory scale experiments showing growth of the fungi on papaya cellulosic material and sugarcane bagasse within 4 days of inoculation. Initial microscopic observations indicate approximately 30% oil/cell.

The third objective is to utilize biofuel in anaerobic digesters that could be adapted to the farm scale level in Hawaii. Anaerobic digesters are ideal for utilizing waste streams because the output of this process results in production of energy, fertilizer, and value added products. Albizia is an invasive tree throughout the Pacific islands that would be an abundant feedstock source. Collaborative research with the USDA Forestry and the University of Hawaii at Hilo, has used high-resolution satellite imagery and geospatial and remote sensing software to map the current spread of albizia in the Hilo and Puna districts on the island of Hawaii. This albizia detection technology will be extended to measure albizia stands throughout the state of Hawaii. We will utilize albizia as a potential feedstock, identifying other feedstocks and optimizing conditions that selected microbes will efficiently digest feedstock combinations under anaerobic conditions. Albizia and agricultural sweet potato and taro waste products have been sent to the Ohio State University for biochemical analysis to determine methane potential under anaerobic conditions.

These activities support objective 1 of the inhouse parent project, "Efficiently and effectively conserve, backup, regenerate and evaluate tropical/subtropical fruit and nut genetic resources and distribute samples and associated information worldwide".


Last Modified: 10/25/2014
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